CN202050362U - Output voltage self-adjusting circuit structure of peak current circuit - Google Patents

Abstract

The utility model relates to an output voltage self-adjusting circuit structure of peak current circuit, comprising an operational amplifier, wherein output end of the operational amplifier is connected with the grid end of a third MOS transistor, the source end of the third MOS transistor is connected with the inverting end of the operational amplifier and then is grounded through a first resistor, and the drain end of the third MOS transistor is respectively connected with the drain end of a first MOS transistor, the grid end of the first MOS transistor and the grid end of the second MOS transistor; the source ends of the first MOS transistor and the second MOS transistor are correspondingly connected and then connected with a power supply IDC, and the other end of the power supply IDC, relative to the end connected with the source end of the second MOS transistor, is connected with the drain end of the second MOS transistor; and the drain end of the second MOS transistor is grounded through a second resistor. The circuit structure is simple in structure, convenient in adjustment, safe and reliable, safe use of a converter is ensured, the service life of the converter is extended, and the use cost of the converter is lowered.

Description

The self-regulating circuit structure of peak current circuit output voltage

Technical field

The utility model relates to a kind of circuit structure, especially the self-regulating circuit structure of a kind of peak current circuit output voltage, specifically be used for the self-regulating circuit structure of current-mode DC-DC converter peak current circuit output voltage, belong to the technical field of current-mode DC-DC converter.

Background technology

The DC-DC converter can be divided into two types of voltage-mode and current-mode according to the feedback system that is adopted.Wherein, Voltage Feedback control is the most basic a kind of control technology of Switching Power Supply, belongs to the monocycle feedback controling mode.Voltage Feedback control only realizes the negative feedback of entire circuit by a voltage feedback signal, have only a feedback control loop in the The whole control circuit, is a kind of monocycle control system.Current Control can be divided into average current and peak current FEEDBACK CONTROL, because the gain of average current FEEDBACK CONTROL current amplifier at the switching frequency place has maximum constraints, and parameter designing debugging such as two closed loop amplifier bandwidth, gain are complicated, therefore seldom adopt in practice.Usually said Current Feedback Control all is a peak current FEEDBACK CONTROL.Peak current circuit in the DC-DC converter can be avoided the excessive damage that causes of entire circuit electric current, but the corresponding peaks current circuit generally can design a fixing peak current limit, but the maximum load current of general peak current electric current restriction during than the entire circuit operate as normal is all much bigger.And switching tube conducting resistance and the heat radiation of whole converter power consumption etc. are generally all considered according to the real work load current.But be operated in unusual condition when converter, for example during short circuit, remain on peak inrush current work in the time of the president, then can cause the damage of converter, influence the normal use of converter.

Summary of the invention

The purpose of this utility model is to overcome the deficiencies in the prior art, provides a kind of peak current circuit output voltage self-regulating circuit structure, and it is simple in structure, easy to adjust, guarantee the safe in utilization of converter, reduce the use cost of converter, safe and reliable.

The technical scheme that provides according to the utility model, the self-regulating circuit structure of described peak current circuit output voltage, comprise operational amplifier, the output of described operational amplifier links to each other with the gate terminal of the 3rd metal-oxide-semiconductor, the source terminal of the 3rd metal-oxide-semiconductor links to each other the back by first grounding through resistance with the end of oppisite phase of operational amplifier, the drain electrode end of the 3rd metal-oxide-semiconductor links to each other with the drain electrode end of first metal-oxide-semiconductor, the gate terminal of first metal-oxide-semiconductor and the gate terminal of second metal-oxide-semiconductor respectively; The corresponding back that links to each other with the source terminal of second metal-oxide-semiconductor of first metal-oxide-semiconductor links to each other with power supply IDC, and power supply IDC links to each other with the drain electrode end of second metal-oxide-semiconductor corresponding to the other end that links to each other with the second metal-oxide-semiconductor source terminal; The drain electrode end of second metal-oxide-semiconductor is by second grounding through resistance.

The in-phase end of described operational amplifier is feedback voltage input FB.Described first metal-oxide-semiconductor, second metal-oxide-semiconductor and the 3rd metal-oxide-semiconductor are P type metal-oxide-semiconductor.

Advantage of the present utility model: the corresponding back that links to each other with the 3rd metal-oxide-semiconductor M3 of operational amplifier forms voltage follower, and the in-phase end of operational amplifier is accepted load feedback voltage V _FB, the drain electrode end of the 3rd metal-oxide-semiconductor M3 links to each other load feedback voltage V with the drain electrode end of the first metal-oxide-semiconductor M1, the gate terminal of the first metal-oxide-semiconductor M1 and the gate terminal of the second metal-oxide-semiconductor M2 _FBThe electric current I 1 that produces obtains electric current I 2 after by the first metal-oxide-semiconductor M1 and the second metal-oxide-semiconductor M2 mirror image, and with power supply IDC corresponding matching after generation voltage Vcalmp; Sample rate current in described voltage Vcalmp and the peak current circuit is the linear changing relation, therefore can control the upset that the PWM comparator is exported by peak current circuit output voltage and voltage Vcalmp after relatively, can control the user mode of whole DC-DC converter, avoiding the DC-DC converter to drive load works long hours in the peak inrush current state, guarantee the safe in utilization of DC-DC converter, reduced the use cost of DC-DC converter, increased the service life, safe and reliable.

Description of drawings

Fig. 1 is circuit theory diagrams of the present utility model.

Description of reference numerals: 1-operational amplifier.

Embodiment

The utility model is described in further detail below in conjunction with concrete drawings and Examples.

As shown in Figure 1: in order to regulate automatically to the peak current circuit output voltage, the utility model comprises operational amplifier 1, the output of described operational amplifier 1 links to each other with the gate terminal of the 3rd metal-oxide-semiconductor M3, the end of oppisite phase of operational amplifier 1 links to each other with the source terminal of the 3rd metal-oxide-semiconductor M3, and the in-phase end of operational amplifier 1 forms feedback voltage input FB; Operational amplifier 1 is connected the back and forms voltage follower with the 3rd metal-oxide-semiconductor M3.The source terminal of the 3rd metal-oxide-semiconductor M3 is by first resistance R, 1 ground connection, and the drain electrode end of the 3rd metal-oxide-semiconductor M3 links to each other with the drain electrode end of the first metal-oxide-semiconductor M1, the gate terminal of the first metal-oxide-semiconductor M1 and the gate terminal of the second metal-oxide-semiconductor M2.The gate terminal of the first metal-oxide-semiconductor M1 links to each other with the gate terminal of the second metal-oxide-semiconductor M2, thereby forms image source between the first metal-oxide-semiconductor M1 and the second metal-oxide-semiconductor M2.The first metal-oxide-semiconductor M1 is corresponding with the source terminal of the second metal-oxide-semiconductor M2 to link to each other, and link to each other with the end of power supply IDC, power supply IDC links to each other with the drain electrode end of the second metal-oxide-semiconductor M2 corresponding to the other end that links to each other with the second metal-oxide-semiconductor M2 source terminal, the drain electrode end of the second metal-oxide-semiconductor M2 and power supply IDC intersect at the Y point, and by second resistance R, 2 ground connection.The first metal-oxide-semiconductor M1, the second metal-oxide-semiconductor M2 and the 3rd metal-oxide-semiconductor M3 are P type metal-oxide-semiconductor.Power supply IDC can be current source or voltage source.

During use, the feedback voltage input FB and the feedback voltage V of operational amplifier 1 _FBLink to each other described feedback voltage V _FBObtain by the sampling to load voltage when carrying for DC-DC converter band, generally can suppose to sample by sample resistance obtains feedback voltage V _FBWork as feedback voltage V _FBAfter loading on the in-phase end of operational amplifier 1, because operational amplifier 1 forms voltage follower, operational amplifier 1 can produce electric current I 1 when making the 3rd metal-oxide-semiconductor M3 conducting, and described electric current I 1 can be expressed as:

$I1=\frac{V_{\mathrm{FB}}}{R1}---\left(1\right)$

Because the first metal-oxide-semiconductor M1 and the second metal-oxide-semiconductor M2 form image source, and the breadth length ratio of the first metal-oxide-semiconductor M1 and the corresponding conducting channel of the second metal-oxide-semiconductor M2 can be set arbitrarily, therefore here the breadth length ratio of supposing the first metal-oxide-semiconductor M1 and the corresponding conducting channel of the second metal-oxide-semiconductor M2 is 1: 1, can obtain the current value identical with electric current I 1 at the drain electrode end of the second metal-oxide-semiconductor M2; Also be

I2＝I1 (2)

Therefore, the electric current I 2 that flows through the second metal-oxide-semiconductor M2 drain electrode end produces correspondent voltage value Vclamp with power supply at the Y point, and then Vcalmp can be expressed as:

$\mathrm{Vclamp}=\frac{R2}{R1}*V_{\mathrm{FB}}+V_{\mathrm{DC}}---\left(3\right)$

This voltage Vcalmp that is to say in the current-mode DC-DC converter and be input to the maximum peak voltage value of PWM comparator input terminal when load is in big current work.In order to guarantee the safety of DC-DC converter, an end of PWM comparator links to each other with the peak current circuit.The peak current circuit is used for the current sample of DC-DC converter driving respective load and is input to the other end of PWM comparator after being converted to voltage, when the magnitude of voltage of peak current circuit output equates with Vcalmp, the PWM comparator is to PWM controller output control signal corresponding, the safe in utilization of DC-DC converter guaranteed in the output that makes the PWM controller turn-off whole DC-DC converter.

Particularly, suppose that the voltage that the peak current circuit is exported is V _P, when ignoring the slope compensation amount, can be with V _PBe expressed as:

V _P＝I _P*R _S (4)

Wherein, I _PBe filter inductance electric current, R _SBe sampling resistor.

As voltage Vclamp and voltage V _PWhen voltage was identical, the PWM comparator overturn, and also promptly reached the electric current restriction of current-mode DC-DC converter; At this moment, have

$\frac{R_2}{R_1}*V_{\mathrm{FB}}+V_{\mathrm{DC}}=I_P*R_S---\left(5\right)$

Can access

$I_P=\frac{\frac{R_2}{R_1}*V_{\mathrm{FB}}+V_{\mathrm{DC}}}{R_S}=\frac{R_2}{R_S*R_1}*V_{\mathrm{FB}}+\frac{V_{\mathrm{DC}}}{R_S}---\left(6\right)$

By following formula (6) as can be known, the filter inductance electric current I of sampling and obtaining _PAlong with load feedback voltage V _FBLinear change.Therefore,, the DC-DC converter works long hours when peak inrush current is worked when driving load, and can be according to load feedback voltage V _FBBetween voltage follow, thereby realized the dynamic adjustments of peak current, and turn-off whole converter by the upset of PWM comparator output, guarantee the safe in utilization of whole converter.Sampled voltage I when the peak current circuit _PFollow load welding block voltage V _FBAfter the linear change, the output of peak current circuit also can be followed corresponding variation, guarantees to make the upset of PWM comparator output, reaches the operating state by the upset control DC-DC converter of PWM comparator output state.When considering the slope compensation amount in the reality, the filter inductance electric current I _PWith load feedback voltage V _FBEqually also keep the corresponding linear relation.

The corresponding back that links to each other with the 3rd metal-oxide-semiconductor M3 of the utility model operational amplifier 1 forms voltage follower, and the in-phase end of operational amplifier 1 is accepted load feedback voltage V _FB, the drain electrode end of the 3rd metal-oxide-semiconductor M3 links to each other load feedback voltage V with the drain electrode end of the first metal-oxide-semiconductor M1, the gate terminal of the first metal-oxide-semiconductor M1 and the gate terminal of the second metal-oxide-semiconductor M2 _FBThe electric current I 1 that produces obtains electric current I 2 after by the first metal-oxide-semiconductor M1 and the second metal-oxide-semiconductor M2 mirror image, and with power supply IDC corresponding matching after generation voltage Vcalmp; Sample rate current in described voltage Vcalmp and the peak current circuit is the linear changing relation, therefore can control the upset that the PWM comparator is exported by peak current circuit output voltage and voltage Vcalmp after relatively, can control the user mode of whole DC-DC converter, avoiding the DC-DC converter to drive load works long hours in the peak inrush current state, guarantee the safe in utilization of DC-DC converter, reduced the use cost of DC-DC converter, increased the service life, safe and reliable.

Claims (3)

1. self-regulating circuit structure of peak current circuit output voltage, it is characterized in that: comprise operational amplifier (1), the output of described operational amplifier (1) links to each other with the gate terminal of the 3rd metal-oxide-semiconductor (M3), the source terminal of the 3rd metal-oxide-semiconductor (M3) links to each other the back by first resistance (R1) ground connection with the end of oppisite phase of operational amplifier (1), the drain electrode end of the 3rd metal-oxide-semiconductor (M3) links to each other with the drain electrode end of first metal-oxide-semiconductor (M1), the gate terminal of first metal-oxide-semiconductor (M1) and the gate terminal of second metal-oxide-semiconductor (M2) respectively; The corresponding back that links to each other with the source terminal of second metal-oxide-semiconductor (M2) of first metal-oxide-semiconductor (M1) links to each other with power supply IDC, and power supply IDC links to each other with the drain electrode end of second metal-oxide-semiconductor (M2) corresponding to the other end that links to each other with second metal-oxide-semiconductor (M2) source terminal; The drain electrode end of second metal-oxide-semiconductor (M2) is by second resistance (R2) ground connection.

2. according to the self-regulating circuit structure of the described peak current circuit output voltage of claim 1, it is characterized in that: the in-phase end of described operational amplifier (1) is feedback voltage input FB.

3. according to the self-regulating circuit structure of the described peak current circuit output voltage of claim 1, it is characterized in that: described first metal-oxide-semiconductor (M1), second metal-oxide-semiconductor (M2) and the 3rd metal-oxide-semiconductor (M3) are P type metal-oxide-semiconductor.

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